The Annual Meeting of the American Society of Clinical Oncology (ASCO) was held at McCormick Place June 3-7, 2011, in Chicago, Illinois. The ASCO meeting is the premier educational and scientific event in the oncology community, highlighting the most advanced treatments, products, and services in cancer care.

More than 30,000 cancer specialists from around the world gathered at the 2011 ASCO Annual Meeting to discuss the latest innovations in research, quality, practice and technology in cancer. This meeting is the platform for the release of thousands of scientific abstracts -- highly anticipated research news for many people, including patients, caregivers, and the general public. News announced during the meeting includes the latest findings from cancer clinical trials, including new drug studies that could change current standards of care.

Pharmacokinetic studies of [3H]oleandrin, a cardiac glycoside component of AnvirzelTM, were conducted in mice after either an i.v. dose (40 μ g/kg) or a p.o. dose (80 μ g/kg). Oleandrin was rapidly absorbed after oral dosing (Cmax at 20 min) although the elimination half life was longer (2.3 ± 0.5 h) than that after i.v. dosing (0.4 ± 0.1 h). The AUC0-co values obtained after i.v. and p.o. dosing were 24.6 ± 11.1 and 14.4 ± 4.3 [(ng/ml)h], respectively, resulting in an oral bioavailability of approximately 30%. After i.v. administration, oleandrin concentration in liver was approximately twice that measured in heart or kidney tissue. Oleandrigenin, the aglycone of oleandrin, was also found in these tissues. At 5 min, >60% of the total radioactivity in liver was due to oleandrin while 28% of the given dose was present as oleandrigenin. Twenty-four hours following injection, 8% of total radioactivity was excreted in urine and contained both oleandrigenin (4.4% of the injected dose) and oleandrin (1.9%). Sixty-six percent of injected radioactivity was found in feces and consisted of oleandrin and oleandrigenin in equal amounts. Uptake of oleandrin in brain after i.p. injection of oleandrin (3 mg/kg) or oleander extract (700 mg/kg) was examined. Measured by LC/MS/MS, oleandrin content in brain was higher following injection of extract than it was with an equivalent dose of oleandrin. The data suggest that components within oleander extract may enhance transport of oleandrin across the blood brain barrier.

Cardiac glycosides such as digitoxin and ouabain have previously been shown to be selectively cytotoxic to tumor as opposed to normal cells. Moreover, this class of agents has also been shown to act as potent radiosensitizers. In the present study we explored the relative radiosensitization potential of oleandrin, a cardiac glycoside contained within the plant extract known as AnvirzelTM that recently underwent a Phase I trial as a novel drug for anticancer therapy. The data show that oleandrin produces an enhancement of sensitivity of PC-3 human prostate cells to radiation; at a cell survival of 0.1, the enhancement factor was 1.32. The magnitude of radiosensitization depended on duration of exposure of cells to drug prior to radiation treatment. While a radiosensitizing effect of oleandrin was evident with only 1 h of cell exposure to drug, the effect greatly increased with 24 h oleandrin pretreatment. Susceptibility of PC-3 cells to oleandrin and radiation-induced apoptosis was dependent on activation of caspase-3. Activation was greatest when cells were exposed simultaneously to oleandrin and radiation. Inhibition of caspase¬3 activation with Z-DEVD-FMK abrogated the oleandrin-induced enhancement of radiation response suggesting that both oleandrin and radiation share a caspase-3 dependent mechanism of apoptosis in the PC-3 cell line.

Initial identification and characterization of the major biochemical and biological properties of AnvirzelTM, a patented hot-water extract of Nerium oleander, were undertaken using HPLC, LC/MS, and in vitro cell growth inhibition assays. Analyses using high pH anion exchange chromatography with electrochemical detection consistently revealed seven major polysaccharide peaks which were subsequently designated as a "carbohydrate fingerprint." Analyses of monomer sugar composition revealed glucose and galacturonic acid as major carbohydrate residues, while carbohydrate linkage studies identified glucopyranosyl and 6-glucopyranosyl as major terminal carbohydrate residues. Nonpolar compounds were separated from polar components through solid phase extraction and analyzed by both reverse phase HPLC and LC/MS methods. Two nonpolar cytotoxic components, oleandrin and its aglycone, oleandrigenin, were detected. Quantitative analysis showed that the oleander extract contained oleandrin and oleandrigenin at concentrations of 2.5 and 4.4 μ g/mg extract, respectively. Five proteins with molecular weights of 6, 20, 35, 68, and 150 kD were also identified in the oleander extract although their functions remain unknown. Cytotoxicity studies showed oleandrin to be a potent growth inhibitory compound against human melanoma BRO cells with an IC50 of 4.0 ng/ml. In the same test system, the IC50 values for oleandrigenin and the complete oleander extract against human melanoma cells were 17.0 ng/ml and 1.6 (μg/ml, respectively. This initial characterization and pharmacology research has served as a basis for quality control studies for the production and subsequent clinical Phase I trial of AnvirzelTM .

AnvirzelTM is an extract of Nerium oleander currently undergoing Phase I clinical evaluation as a potential treatment for cancer. Two of the active components of AnvirzelTM are the cardiac glycosides oleandrin and oleandrigenin. Previous studies have demonstrated that, in vitro, cardiac glycosides may inhibit fibroblast growth factor-2 (FGF-2) export through membrane interaction with the Na+,K+-ATPase pump. In continuing research on the antitumor activity of this novel plant extract, the relative abilities of oleandrin and oleandrigenin to inhibit FGF-2 export from two human prostate cancer cell lines, DUl45 and PC3, were examined. An ELISA assay was utilized to determine the FGF-2 concentration in the cell culture medium before and after exposure to cardiac glycosides or the parent extract material AnvirzelTM . Both cell lines were exposed to non-cytotoxic concentrations of oleandrin (0.05 and 0.1 ng/mL) for up to 72 hr. Studies also were conducted with AnvirzelTM and ouabain. Oleandrin (0.1 ng/mL) produced a 45.7% inhibition of FGF-2 release from PC3 cells and a 49.9% inhibition from DU145 cells. Non-cytotoxic concentrations (100 ng/mL) of AnvirzelTM produced a 51.9 and 30.8% inhibition of FGF-2 release, respectively, in the two cell lines. The decrease in FGF-2 release from cells required continuous incubation for 48-72 hr; shorter incubation times were not effective. These results demonstrate that AnvirzelTM , like oleandrin, inhibited FGF-2 export in vitro from PC3 and DUI45 prostate cancer cells in a concentration- and time-dependent fashion and may, therefore, contribute to the antitumor activity of this novel treatment for cancer.

Anvirzel™ (oleander extract) is a novel antitumor compound extracted from a flowering plant, N. oleander, belonging to the family Apocynaceae. Anvirzel™ consists of several compounds, including complex polysaccharides, proteins and individual sugars. It contains non-water soluble compounds, and two of these have been specifically identified by molecular weight and fragmentation characterization as Oleandrin and Oleandrigenin (Newman et al., unpublished observations). These two compounds of Anvirzel™, and possibly a third one, are cytotoxic. In the present studies, we examined the cytotoxicity of Anvirzel™ and Oleandrin on cancer cell lines of human, murine and canine origin. Our results from tests on cultures of two human prostate cancer cell lines, PC-3M and C4-2, and a murine melanoma cell line, K1735-X21, treated with Anvirzel™ and Oleandrin indicate several novel features: (i) neither Anvirzel™ nor Oleandrin showed any cytotoxic effect on murine melanoma K1735-X21 cells, (ii) when using even low drug concentrations human prostate cancer PC-3M cells showed significant susceptibility to cell killing, (iii) the cell killing is apparently mediated through the loss of telomeric DNA, followed by the arrest of cells in G2/M phase, induction of endomitosis, extensive DNA fragmentation, reduced levels of TRF2 and finally cell death, (iv) FACS analysis revealed induction of cell death in a dose and duration dependent manner in the human PC-3M cell line, followed by a saturation effect.

In earlier studies, Anvirzel™ was shown to have toxic effects on cells, decreasing the level of fibroblast growth factor-2. 15 Whether Anvirzel™ and its derivative Oleandrin exert their cytotoxic effects through inducing aberrations of chromosome morphology, polyploidy and cell death is not known. Because Anvirzel™ is known to have antitumor activity, we investigated the mechanism of cancer cell death in a variety of cancer cell lines of human, murine and canine origin. Our results show that both AnvirzelTM and Oleandrin are potent cell death inducers in two human prostate cancer cell lines.

Also interesting was the finding of a loss of telomere length and its correlation with TRF2 levels in the different cancer cell lines after their treatment with Anvirzel™.

A role for TRF2 has been implicated in telomere loss and end-to-end fusion of chromosomes leading to apoptosis; these results thus suggest that Anvirzel™-induced cell killing may be caused by the reduced levels of TRF2 in these cell lines and TRF2 reduction may be one mechanism of action whereby these drugs induce cancer cell apoptosis.

Conclusion

This study has shown that, in vitro, both Anvirzel™ and its derivative compound Oleandrin are highly cytotoxic to human prostate cancer cells.

Finally, Anvirzel™ and Oleandrin both have the potential to be used in chemotherapy for a variety of human cancer types. Studies evaluating such therapies are in progress at our Cancer Center.

Cardiac glycosides are used clinically to increase contractile force in patients with cardiac disorders. Their mechanism of action is well established and involves inhibition of the plasma membrane Na+ /K+ -ATPase, leading to alterations in intracellular K+ and Ca2+ levels. Here, we report that the cardiac glycosides oleandrin, ouabain, and digoxin induce apoptosis in androgen-independent human prostate cancer cell lines in vitro. Cell death was associated with early release of cytochrome c from mitochondria, followed by proteolytic processing of caspases 8 and 3. Oleandrin also promoted caspase activation, detected by cleavage poly (ADP-ribose) polymerase and hydrolysis of a peptide substrate (DEVD-pNA). Comparison of the rates of apoptosis in poorly metastatic PC3 M-Pr04 and highly metastatic PC3 M-LN4 subclones demonstrated that cell death was delayed in the latter because of a delay in mitochondrial cytochrome c release. Single-cell imaging of intracellular Ca2+ fluxes demonstrated that the proapoptotic effects of the cardiac glycosides were linked to their abilities to induce sustained Ca2+ increases in the cells. Our results define a novel activity for cardiac glycosides that could prove relevant to the treatment of metastatic prostate cancer.

Agents that can suppress the activation of nuclear factor-kB (NF-kB) and activator protein-l (AP-l) may be able to block tumorigenesis and inflammation. Oleandrin, a polyphenolic cardiac glycoside derived from the leaves of Nerium oleander, is a candidate NF-kB and AP-l modulator. We investigated the effect of oleandrin on NF-kB activation induced by inflammatory agents. Oleandrin blocked tumor necrosis factor (TNF)-induced activation of NF-kB in a concentration- and time-dependent manner. This effect was mediated through inhibition of phosphorylation and degradation of IkB α, an inhibitor of NF-kB. A proprietary hot water extract of oleander (AnvirzelTM) also blocked TNF-induced NF-kB activation; subsequent fractionation of the extract revealed that this activity was attributable to oleandrin. The effects of oleandrin were not cell type specific, because it blocked TNF-induced NF-kB activation in a variety of cells. NF-kB-dependent reporter gene transcription activated by TNF was also suppressed by oleandrin. The TNF -induced NF-kB activation cascade involving TNF receptor l/TNF receptor-associated death domain/TNF receptor-associated factor 2/NF-kB-inducing kinase/IkB α kinase was interrupted at the TNF receptor-associated factor 2 and NF-kB-inducing kinase sites by oleandrin, thus suppressing NF-kB reporter gene expression. Oleandrin blocked NF-kB activation induced by phorbol ester and lipopolysaccharide. Oleandrin also blocked AP-l activation induced by TNF and other agents and inhibited the TNF-induced activation of c-Jun NH2-terminal kinase. Overall, our results indicate that oleandrin inhibits activation of NF-kB and AP-l and their associated kinases. This may provide a molecular basis for the ability of oleandrin to suppress inflammation and perhaps tumorigenesis.